Double-Angle and Half-Angle Identities

Using the second identity, find Cos(50)

• sin²(25) - cos²(25) 
• cos²(50) - sin²(50)
• cos²(25) - sin²(25)
• sin²(50) - cos²(50) 

Find the exact value of sin 2x if sin x = 12/13 and x is in the first quadrant. 

• 120/169
• 25/169
• 60/169
• 5/13

Use a double-angle identity to find the exact value of each expression
cos θ = 4/5 and 270° < θ < 360°
Find sin 2θ

• -1/5
• 24/25
• -24/25
• -25/24

Using the third identity, find Cos(40)

• 2cos² (40) - 1
• 2cos² (20) - 1
• 2cos² (20) + 1
• 2cos² (40) + 1

Which identity represents a double-angle identity for sin 2θ?

• 2sinθcosθ
• cos²θ - sin²θ
• 1 - 2sin²θ
• 2cos²θ - 1

Use a double-angle or half-angle identity to find the exact value of each expression

cos θ = 4/5 and 270° < θ < 360°Find sin 2θ

• -1/5

• 24/25

• -24/25

• -25/24

Using the fourth identity, find Cos(120)

• 1-2sin²(120)
• 1+2sin²(120)
• 1+2sin²(60)
• 1-2sin²(60)

sin2u =

• (sinu)(cosu)
• 2(sinu)(cosu)
• (sinu)^2
• 2(sinu)^2

cos2u =

• 2(sinu)(cosu)
• (cosu)^2 - (sinu)^2
• 2(cosu)^2 - 2
• (sinu)^2 - (cosu)^2

Use a double-angle identity to find the exact value of each expression
cos θ = 4/5 and 270° < θ < 360°
Find sin 2θ

• -1/5
• 24/25
• -24/25
• -25/24